Stabilized potential and current sources



M y 3 1967 s. GREENBERG ET AL 3,323,033

STABILIZED POTENTIAL AND CURRENT SOURCES Filed June 5, 1963 INVENTORS SOL GREENBERG IRVING FORREST BY ATTOR ews 3,323,038 STABILIZED POTENTIAL AND CURRENT SOURCES Sol Greenberg, 23 Ridge Drive, Port Washington, N.Y. 11050, and Irving Forrest, 21 Evelyn Road, Plainview, N.Y. 11803 Filed June 5, 1963, Ser. No. 285,632 12 Claims. (Cl. 323-22) This invention relates to open loop stabilized sources of direct current and potential for use as DC. power supplies and as reference sources in power supplies and other equipment.

There are presently known to the art a wide variety of vacuum tube and solid-state constant current and potential sources ranging from simple zener diode circuits to series and shunt regulators employing an externally closed and basically degenerative loop. The complexity of the circuit varies somewhat in relation to operating requirements, general purpose and high capacity supplies being considerably more complex than fixed purpose or low power sources.

Circuit complexity is also afunction of the required degree of constancy or regulation in the presence of temperature, line and load fluctuations. Where a simple zener diode circuit, with or without a transistor to form a constant current amplifier cannot meet these requirements, it is generally the practice to employ closed loop series or shunt regulators. The latter, besides being complex and expensive per se, are generally prone to instability problems requiring added complexity and expense by way of stabilizing schemes.

It is thus an object of the invention to provide a source of constant voltage or current which preserves the open loop simplicity of simple circuit sources while providing regulation and stability not otherwise attainable in such circuits.

These and other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities, combinations, and improvements pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

Serving to illustrate an exemplary embodiment of the invention is the sole figure illustrating in schematic form a circuit adapted to supply a plurality of stabilized D.C. outputs.

As seen in the figure, an AC. potential is developed across the secondary winding SW of a transformer T which is energized from a primary winding P The primary is excited via a power switch S from an alternating current source. The potential across the secondary is converted to a unidirectional voltage, illustratively by means of a full wave circuit which includes rectifiers CR and CR in full wave configuration; the circuit also includes a filter capacitor C7. The relatively unregulated DC. voltage appearing across capacitor C is connected to and appears across output terminals E and E which may supply a circuit not requiring a regulatedoutput.

Energized by the potential E -E-; are two branches R CR and R R CR is a forwardly conducting silicon junction diode utilized for reasons hereinafter noted. The branches R CR and R R supply energizing potential for a transistor Q Thus the base of transistor Q is connected to the junction of R and CR While the emitter thereof connects to the junction of R and R With this circuit arrangement, the voltage across R tends to equal the somewhat constant voltage across CR Hence the emitter current,

United States Patent 3,323,038 Patented May 30, 1967 and therefore the collector current, of Q tends to be constant. The use of CR instead of a zener diode has the advantage in this circuit of providing a measure of ambient temperature compensation since the thermal characteristics of CR tend to compensate for the similar characteristics in the base-emitter junction of Q The effect of the connection which includes R is to introduce into the base-emitter of Q a corrective signal which compensates for the fact that the impedance of CR although relatively low is not zero whence line voltage fluctuations appear in attenuated form in the emitter-base circuit of Q unless this compensation is provided. The effect of this connection also functions to minimize temperature fluctuations in Q resulting from E E voltage variations and not compensated by CR Proportioning of R and R may also be utilized to provide over-compensation. The overall circuit thus far described is thus seen to provide a relatively stable, substantially constant current in the collector of Q It may be observed that the circuit thus far described.

appears topograp-hically similar to conventional error detector stages in many closed loop regulators. In such stages there is frequently provided a voltage reference branch and an output sampling branch to which are connected the emitter-base circuit of an error detecting transistor. However, in these arrangements the elements are chosen so that the emitter-base potential, and thus the emitter-collector current, varies in accordance with output voltage fluctuations. In contradiction, the circuit herein described is designed to do the very opposite, i.e., maintain the emitter-base potential and emitter-collector current constant in spite of variations in the supply voltage.

The constant collector current in Q also flows in the reverse current direction through CR preferably a temperature compensated zener diode, and also through CR these elements being in series and connected in a branch from the collector of Q; to terminal E this branch also includes R in serial relation and the seriesparallel network CR CR and R The constant current through zener diode CR supplements the inherently and relatively constant voltage characteristic of the zenerdiode, thereby providing a constant voltage across CR which'has stability improved over that provided by conventional zener diode circuits and so called constant current circuitsl" Energized by the collector output of stage Q, is a further stage Q,- in emitter-follower relationship. The emitter base circuit of this stage is temperature stabilized with the aid of CR the ambient thermal characteristics of which tend to offset the similar characteristics in the base-emitter junction of Q The stabilized emitter-current of stage Q flows from E through the combination R C 14, CR in part through zener diode CR and resistor R and in part througha branch paralleling CR and R and comprising R14 R R and R the first and last-mentioned being conveniently variable. These branches, in response to the emitter-current of Q produce highly stabilized voltages, especially the voltage E -E dropped across CR As previously noted, temperature stability of the baseemitter of Q is aided by the presence of CR which has similar thermal characteristics. However, in maintaining a constant current in its emitter circuit, the emitter-collector voltage of Q; will tend to vary in the presence of disturbances. As a consequence, the power dissipation of Q; will tend to vary causing a related change in the thermal characteristics of Q which would not fully be compensated 'by CRIZ.

To overcome this difficulty, there is connected across the emitter-collector of Q the base-emitter circuit of a further stage Q The collector of Q, is returned through R to E the emitter is connected to E via R which is also common to the emitter Q The tendency of the emitter-collector potential of Q; to change is thus counteracted by the corrective action of Q A tendency toward voltage change in the emittercollector of Q produces a change in the emitter-current of Q thus producing a voltage change across R which tends to offset the assumed change in Q Transistors Q and Q are of opposite conductivity type; further Q and Q; are preferably germanium and silicon types, respectively, although Q17 may be germanium provided an extra diode is added to the circuit. By this arrangernent, the operation of both transistors Within their correct dynamic range is assured.

The emitter-current of Q; is thus seen to be a highly stabilized parameter which may be used per se as a current source and which also produces correspondingly stabilized output potentials E E E E and E E The latter two are conveniently adjustable by varying R and R16.

Other potentials may also be provided, such as E E E E il -E E3-Eq, E E and other combinations. The use of these potentials in a general purpose closed loop supply is illustrated in a copending application assigned to the assignee of the instant application, filed June 5, 1963, and having Ser. No. 285,780, and of which the applicants herein are co-inventors.

The invention is not limited to the specific combinations, arrangements and elements herein shown and described as the art will recognize modifications thereof. Departures may thus be made from the foregoing without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A substantially constant D.C. source comprising a source of unregulated D.C. energy,

a transistor including a base, emitter and collector; circuit means connected across the emitter-base circuit of said transistor including a diode means having thermal characteristics related to the thermal characteristics of the emitter-base junction of said transistor for supplying a reference potential to the emitter-base circuit of said .transistor, and resistance connected to said diode means for providing a potential which compensates for the variations in said reference potential due to the dynamic impedance of said diode means;

a first circuit branch means connected across said source and including said diode means to energize said diode means and develop said reference potential;

a second circuit branch means connected across said source and including said resistance for developing said compensating potential as a function of the potential across said source; and

a third circuit branch means connected across said source and including the emitter-collector circuit of said transistor, said third circuit branch being characterize-d by a substantially constant current flow therethrough.

2. A substantially constant D.C. source in accordance with claim 1 wherein said diode means is selected having a temperature coefficient essentially the same as the temperature coefficient of the emitter-base junction of said transistor, wherein said diode means is energized to provide said reference potential while operating in its forward conducting region, and wherein said diode means is so connected that said reference potential is in opposition to the potential developed across the emitter-base junction of said transistor.

3. A substantially constant voltage source comprising a substantially constant current source in accordance with claim 1 and a Zener diode connected in said third circuit branch means in series with the collector of said transistor, said Zener diode being connected to operate in its Zener region to thereby provide a substantially constant voltage across said Zener diode.

4. A substantially constant D.C. source comprising a source of unregulated D.C. energy,

a transistor including a base, emitter and collector;

circuit means connected across the emitter-base circuit of said transistor including a diode having thermal characteristics related to the thermal characteristics of the emitter-base junction of said transistor for supplying a reference potential to the emitter-base circuit of said transistor, and

a resistance connected in series with said diode for providing a potential which compensates for the variations in said reference potential due to the dynamic impedance of said diode, and which compensates for thermal differences between said diode and said junction,

said diode and said resistance being connected in series between the emitter and base of said transistor so that the net emitter-base potential is substantially stabilized notwithstanding temperature and source voltage changes;

a first circuit branch means connected across said source and including said diode to energize said diode and develop said reference potential;

a second circuit branch means connected across said source and including said resistance for developing said compensating potential as a function of the potential across said source; and

a third circuit branch means connected across said source and including the emitter-collector circuit of said transistor, said third circuit branch being characterized by a substantially constant current flow therethrough; a second transistor including an emitter, base and col lector; circuit means for temperature stabilizing said second transistor;

the emitter-base circuit of said second transistor being in said third circuit branch means and coupled to the collector of said first transistor, and

circuit means connected to the collector-emitter circuit of said second transistor to provide a substan tially constant D.C. output.

5. A substantially constant D.C. source in accordance with claim 4 wherein said diode is selected having a tem= per-ature coefiicient essentially the same as the temperature coefficient of the emitter-base junction of said first transistor, wherein said diode is energized to provide said reference potential while operating in its forward conducting region, and wherein said diode is so connected that said reference potential is in opposition to the potential developed across the emitter-base junction of said first transistor.

6. A substantially constant D.C. source in accordance with claim 4 further including a Zener diode connected in said third circuit branch means to provide a constant potential at the base of said second transistor.

7. A substantially constant D.C. source in accordance with claim 4 further including additional circuit means connected to the emitter-collector circuit of said second transistor to maintain a substantially constant potential across saidernitter-collector circuit of said second transistor.

8. A substantially constant D.C. source in accordance with claim 7 wherein said additional circuit means includes a third transistor including an emitter, base and collector, the emitter-base circuit of said third transistor being con nected across the emitter-collector circuit of said second transistor, a common resistor connected in series with the emitter-collector circuits of said second and third tran sistors'.

9. A source as defined in claim 8 in which said second and third transistors are of opposite conductivity type and are silicon and germanium types, respectively.

10. A substantially constant D.C. source in accordance with claim 6 further including a Zener diode connected in said third circuit branch means to provide a constant potential at the emitter of said second transistor.

11. A substantially constant D.C. source comprising a source of unregulated (D.C. energy,

a transistor including a base, emitter and collector;

circuit means connected across the emitter-base circuit of said transistor including a diode having thermal characteristics related to the thermal characteristics of the emitter-base junction of said transistor for supplying a reference potential to the emitter-base circuit of said transistor, and

a resistance connected in series with said diode for providing a potential which compensates for the variations in said reference potential due to the dynamic impedance of said diode, and which compensates for thermal difierences between said diode and said junction,

said diode and said resistance being connected in series between the emitter and base of said transistor so that the net emitter-base potential is substantially stabilized notwithstanding temperature and source voltage changes;

a first circuit branch means connected across said source and including said diode to energize said diode and develop said reference potential;

a second circuit branch means connected across said source and including said resistance for developing said compensating potential as a function of the potential across said source;

a third circuit branch means connected across said source and including the emitter-collector circuit of said transistor, said third circuit branch being characterized by a substantially constant current flow therethrough;

a second transistor including an emitter, base and collector;

a diode having temperature characteristics related to the temperature characteristics of said second transistor connected in series with the emitter base circuit of said second transistor to provide temperature stabilization;

circuit means connected across the collector-emitter circuit of said second transistor to maintain substantially constant potential thereacross; and

an output circuit including the emitter-collector circuit of said second transistor for providing a substantially constant DC. output.

12. A substantially constant D.C. source in accordance with claim 11 further including a Zener diode connected in said output circuit in series With the emitter-collector circuit of said second transistor.

References Cited UNITED STATES PATENTS 2,693,572 11/1954 Chase. 2,888,633 5/1959 Carter 323- 9 2,979,653 4/1961 Wilcox et al. 3,069,617 12/1962 Mohler. 3,090,905 5/ 1963 Ehret. 3,103,617 9/1963 Schneider.

JOHN F. COUCH, Primary Examiner. W. E. RAY, K. D. MOORE, Assistant Examiners, 

11. A SUBSTANTIALLY CONSTANT D.C. SOURCE COMPRISING A SOURCE OF UNREGULATED D.C. ENERGY, A TRANSISTOR INCLUDING A BASE, EMITTER AND COLLECTER; CIRCUIT MEANS CONNECTED ACROSS THE EMITTER-BASE CIRCUIT OF SAID TRANSISTOR INCLUDING A DIODE HAVING THERMAL CHARACTERISTICS RELATED TO THE THERMAL CHARACTERISTICS OF THE EMITTER-BASE JUNCTION OF SAID TRANSISTOR FOR SUPPLYING A REFERENCE POTENTIAL TO THE EMITTER-BASE CIRCUIT OF SAID TRANSISTOR, AND A RESISTANCE CONNECTED IN SERIES WITH SAID DIODE FOR PROVIDING A POTENTIAL WHICH COMPENSATES FOR THE VARIATIONS IN SAID REFERENCE POTENTIAL DUE TO THE DYNAMIC IMPEDANCE OF SAID DIODE, AND WHICH COMPENSATES FOR THERMAL DIFFERENCES BETWEEN SAID DIODE AND SAID JUNCTION, SAID DIODE AND SAID RESISTANCE BEING CONNECTED IN SERIES BETWEEN THE EMITTER AND BASE OF SAID TRANSISTOR SO THAT THE NET EMITTER- ASE POTENTIAL IS SUBSTANTIALLY STABILIZED NOTWITHSTANDING TEMPERATURE AND SOURCE VOLTAGE CHANGES; A FIRST CIRCUIT BRANCH MEANS CONNECTED ACROSS SAID SOURCE AND INCLUDING SAID DIODE TO ENERGIZE SAID DIODE AND DEVELOP SAID REFERENCE POTENTIAL; A SECOND CIRCUIT BRANCH MEANS CONNECTED ACROSS SAID SOURCE AND INCLUDING SAID RESISTANCE FOR DEVELOPING SAID COMPENSATING POTENTIAL AS A FUNCTION OF THE POTENTIAL ACROSS SAID SOURCE; 